N$7\mathrm{.}8.$ Three functions, F$1,$ F$2,$ and F$3,$ are registered to the netfilter hooks. F$1$ is registered to NF INET POST ROUTING with a priority $-110.$ F$2$ is registered to NF INET LOCAL OUT with a priority $-120.$ F$3$ is registered to NF INET LOCAL OUT with a priority $-100.$ F$4$ is registered to NF INET FORWARD with a priority $-110.$ When we send out an ICMP echo request packet from this machine, which functions will be invoked, and in what order?